If two atoms have different atomic number. are they the same element or an isotope?

Word equation for k(s) +h2o(l) yield koh (aq) + h2

Upon decomposition, one sample of magnesium fluoride produced 1.65 kg of magnesium and 2.56 kg of fluorine. a second sample produced 1.32 kg of magnesium. part a how much fluorine (in grams) did the second sample produce?

Why must sample spots be above the solvent in paper chromatography